Various kinds of work machines such as a bulldozer and a tractor shovel have been often used in working sites for construction, civil engineering and the like. Such kind of the work machine is provided with a blade which is a working attachment. This blade is used widely for bulldozer operation such as digging, carrying of soil, banking, compacting and leveling.
To exert the maximum working efficiency on this work machine, it is important to satisfy various kinds of conditions such as increasing a quantity of soil carried per cycle as much as possible, reducing a resistance during digging/carrying of soil, and fitting to different kinds of soils. Further, ability of banking, compacting and leveling at the same time is preferable because it leads to a remarkable improvement of working efficiency. Finding out an optimum blade structure, configuration, width, height, cutting edge position, cutting angle and the like which satisfy these conditions improves the working efficiency of a work machine, reduces fuel consumption and shortens an entire working period advantageously.
As an example of a blade assembly which increases working amount for this kind of work machine, for example, Japanese Patent No. 2757135, which was proposed by this applicant previously, has been known. This patent publication has disclosed a blade assembly, in which its blade posture provided on a front portion of a large bulldozer can be controlled for each step of digging, carrying of soil, and discharge of soil. The blade assembly disclosed in the same publication controls a blade driving hydraulic system to incline backward (pitch back) the blade at a predetermined angle with respect to a posture at the time of excavation for carrying of soil and incline forward (pitch dump) at a predetermined angle with respect to a posture at the time of digging for discharging of soil.
At the time of carrying of soil, quantity of soil to be embraced within the blade is increased by tipping the blade backward at a predetermined angle with respect to the posture at the time of digging. A force for pressing the ground is generated in a front section of the vehicle by the soil embraced within the blade. The ground contact pressure distribution of tractor belts of the vehicle is equalized by this force so that an apparent vehicle weight is increased and its tractional force is transmitted effectively to the ground. Further, by embracing a large quantity of excavated soil within the blade, the weight of the excavated soil swollen ahead of a blade edge and the ground contact length of the excavated soil on the ground are decreased thereby reducing soil carrying resistance. On the other hand, by tipping forward the blade at a predetermined angle with respect to the posture at the time of digging for discharge of soil, the soil discharge operation is facilitated.
To exert working capacity of a bulldozer to its maximum extent, in terms of force balance on soil carrying operation of the bulldozer, the tractional force must be larger than the soil carrying resistance and vehicle drive force must be larger than the tractional force as described in the above-mentioned publication. According to the above publication, increase in the tractional force and decrease in the soil carrying resistance are made possible by controlling the blade posture, thereby increasing the working amount of the bulldozer. Consequently, the quantity of soil carried can be increased largely without enlarging a bulldozer size, engine output or capacity of its blade.
Most of engine output necessary for digging and carrying of soil in the bulldozer is consumed by drive force of the vehicle and tractional force for digging/carrying of soil. Thus, it is necessary to reduce loss of energy during power transmission to improve fuel consumption efficiency.
Further, the resistance of the blade during digging/carrying of soil needs to be reduced thereby improving the fuel consumption efficiency. Generally, a medium size or small size bulldozer has a shorter soil carrying distance than a large size bulldozer. Thus, the quantity of soil carried is difficult to be increased only by reducing the soil carrying resistance with the art disclosed in the above publication.
If these demands are met, the engine output can be used effectively during digging/carrying of soil even by a blade having the same capacity or the same tractional force as a conventional example.
Because, particularly the medium or small bulldozer is designed to be as compact as possible, its blade is designed with a smaller size as compared to a large bulldozer. The blade assembly disclosed in the above publication is used for the large bulldozer and an extra blade driving hydraulic unit or its attachment needs to be incorporated. Therefore, not only a structure of the entire blade assembly is enlarged but also a number of components is increased, so that a mechanism becomes complicated. Even if it is intended to load the above-described blade assembly on the medium or small bulldozer just as it is, a sufficient installation space for disposing an extremely complicated mechanism is difficult to secure and therefore, the design on the vehicle needs to be changed largely, thereby leading to a large increase in sales price.
On the other hand, according to a blade structure disclosed in Japanese Utility Model Application Laid-Open No. 61-76861, a first blade member is mounted on a front section of a bottom end of a backhoe body and second blade members are mounted on both right and left ends of the first blade member through mounting bolts such that they can be moved to obliquely forward or obliquely backward thereof. According to a blade structure disclosed in Japanese Utility Model Application Laid-Open No. 63-71253, a pair of first blade members for right and left sides are mounted on a front section of a bottom end of a ring mounting type loader through hinges such that they can be swiveled to opposite directions to each other around a vertical axis while a second blade member is mounted on a top edge of each first blade member through hinges such that it can be fallen thereon. Further, according to a blade structure disclosed in the Japanese Utility Model Application Laid-Open No. 4-92064 proposed by the same applicant as the invention, a first blade member is mounted on a front section of a bottom end of an earth-moving machine while a second blade member is protruded from each of right and left end sections of the first blade member such that it is bent forward. Furthermore, Japanese Patent No. 2001-40693 has disclosed a blade structure in which an inclined face for discharging soil and sand remaining on a back face of the blade at the time of leveling work by traveling backward is formed.
The blades disclosed in these publications are called straight dozer, V-dozer, inverted V dozer, U dozer or the like. Those blade faces are produced into various configurations such as an arc face having a certain curvature or a curved face having different curvatures on its upper and lower sections. However, they are not intended clearly for reducing consumption horsepower per tractional force on digging/carrying of soil and increasing power consumption efficiency. As described above, prior arts did not propose any blade which realized effective usage of energy during digging/carrying of soil and low fuel consumption.
Therefore, an object which the invention intends to solve is to provide a blade which is mounted on various kinds of work machines, capable of reducing power consumption due to increase in the quantity of soil per tractional force with a simple structure, realizing low cost by intensifying fuel consumption efficiency, and applicable to work machines for digging, carrying of soil, banking, compacting, leveling and the like.